EXSS 376 1st Edition Final Exam Study Guide Material Post Exam 2 Skeletal System Importance Maximize peak bone mass Prevention and treatment of osteoporosis Prepubescent athletes and exercise Cells Osteoblast builds bone matrix Osteocyte maintains bone tissue Osteoclast breakdown of bone matrix Tissue Lamellar bone o Compact bone 80 of skeleton Provides protection and support Resists stresses produced by weight and movement o Spongy trabecular bone 20 of the skeleton Less weight but still great strength Oriented along lines of stress Comprises almost the entire mature skeleton Highly organized mineralized collagen fibers Quality o Quality strength o Dependent upon balance of action of osteoclasts resorption and osteoblasts formation o Resorption formation INCREASE tissue strength bone mineral density o Bone mineral density measurement Dual energy x ray absorptiometry DEXA Clinical devices to examine BMD Used to examine changes in BMD and monitor osteoporosis Osteopenia 1 2 5 SD below peak bone mass Osteoporosis 2 5 SD below peak bone mass Bone Mass and Aging Peak bone mass is attained in your 20s in both sexes Genetics limits the amount of BMD an individual can attain o Nutritional status o Hormonal status o Activity level Training Wolff s law bone adapts to changes in its mechanical loading o More intense the training the more mechanical loading Key points o Weight bearing or impact loading activities produce GREATER changes in BMD than non weight bearing or weight supported activities o Intensity is MORE important than repetition o Loading is SITE specific o Minimum 6 8 months training are required typically to detect changes in bone mass o Overtraining inadequate rest and recovery and excessive repetitive loads can lead to stress fractures o Training needs to be Population specific Take into account current skeletal health Kids and training o Cannot endure same intensity and volume as adults o Area of risk epiphysis growth plate of long bones strength of cartilage is less than that of bone o Damage to epiphysis can cause it to fuse and result in limb deformity Myths Debunked Misconception resistance training will stunt growth of children Fact NO current evidence of decrease in stature in children who regularly perform resistance exercise in a controlled environment Resistance exercise will have favorable influence on bone growth and development Neuromuscular System Motor Units Functional unit of neuromuscular system Single motor unit single alpha motor neuron and ALL fibers it innervates Skeletal Muscle Structure Epimysium separates muscle from surrounding tissues and organs Perimysium separates muscle into internal compartments fascicles provides conduit for blood vessels and nerves supplying the muscle Endomysium surround each fiber binds each fiber to neighbor satellite cells lie between endomysium and fibers Muscle Fiber T tubules tiny invaginations where action potentials travel INTO muscle SR stores and releases Ca2 from its lateral sacs when excited surround myofibrils Sarcolemma skeletal muscle plasma membrane Fiber Types Alpha motor neuron dictates fiber type properties o Skeletal muscle fibers of any given motor unit are all of the same type o Ex slow twitch motor units will have all SO or Type 1 muscle fibers o However each muscle will have a mixture of all 3 motor units 3 types o Type I slow twitch oxidative Slow fatigue resistant Many mitochondria Red high Mb content Low myosin ATPase activity Small motor unit size Slow conduction velocity contraction speed Low max power o Type IIa fast twitch oxidative glycolytic Fast fatigue resistant more mitochondria than Type IIx o Type IIx fast twitch glycolytic Fast fatigable Cannot change percentage of Type I II o Can change percentage of Type IIa vs IIx o IIx couch potato fibers o Any type of training increase Type IIa Myofibrils Built from 3 proteins o Contractile proteins generate force during contractions Myosin 2 globular heads and single tail Actin helix of single actin proteins o Regulatory proteins help switch contraction on off Tropomyosin long chain covering active binding sites on actin Troponin contains binding site for Ca lifts tropomyosin away from myosin binding sites on actin o Structural proteins help keep contractile proteins actin myosin in proper alignment Contribute to alignment stability elasticity of myofibrils About 12 titin large protein anchoring myosin in middle of sarcomere Striations o W in sarcomere myosin and actin filaments have some degree of overlap w each other called bands o Overlap gives appearance of striations o Sarcomere Z line to Z line o Actin is physically attached to Z line o Myosin is physically attached to M line o Sliding filament theory actin and myosin slide do not change length Sarcomere A band extends entire length of MYOSIN thick filament dArk o Always the same length I band lighter less dense area that just contains ACTIN thin filaments lIght o Contraction shortens H zone contains just MYOSIN and no acting o Shortens during contraction M line middle of sarcomere anchors myosin filaments together at center of sarcomere Nervous System Classes of Neurons Interneurons o 99 of all neurons o Lie entirely in CNS o Integrate afferent and efferent neurons Afferent neurons o Transmit info from receptors TO CNS o Cell body in PNS Efferent neurons o Transmit info from CNS TO effecter cells o Cell body in CNS o Ex alpha motor neuron Action Potentials Voltage gated channels o AP arises at axon hillock o Propagates along axon to axon terminals 5 parts o Resting potential 70 mV Membrane potential is around 80 mV interior of cell still negative For us to create AP must reach 55 mV threshold Size principle recruit smaller slow twitch motor units before larger fast twitch motor units slow twitch motor units resting potential slightly higher Note sodium is OUTSIDE the cell o Rising phase depolarization Membrane reaches threshold and becomes depolarized Na channels open Na enters cell Interior of cell becomes more positive o Overshoot Membrane potential peaks around 30 mV Inside of cell is positive Na channels begin to close K channels open o Falling phase repolarization Rapid repolarization occurs K moves outside cell Inside of cell becomes more negative o Undershoot K channels remain open briefly More K leaves cell Cell becomes hyperpolarized more negative When cell depolarized absolute refractory period prevents another AP from occurring During undershoot phase relative refractory